The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor.
The invention relates in general to aerospike rocket nozzles and in particular to afterburning aerospike rocket nozzles.
Rocket motors are limited in their performance by the energy content of their propellants and the need to carry their oxidizer with them. Rocket motors do, however, provide near-instantaneous thrust and are not limited to atmospheric operation. Jet engines use air to provide their oxidizer, but are either inherently complex (e.g., turbojets and turbofans) or provide no thrust at zero initial speed (ramjets). Because of their use of atmospheric oxygen, jet engines cannot operate in space and take a considerable period of time to xe2x80x9cspool-upxe2x80x9d to full thrust. Jet engines also tend to need substantial levels of maintenance and are quite costly to acquire, maintain and operate. Rocket motors (particularly solid fuel rocket motors) tend to be relatively inexpensive to acquire, require minimal maintenance and virtually nothing to operate.
To try to improve the delivered energy of rocket motors, many methods have been employed. The energy of the fuels and oxidizers have been increased, the nozzles have been contoured and modified to improve their efficiency and the operating pressures have been increased. However, the delivered propellant specific impulse (a measure of the thrust produced per unit mass of propellant) has not appreciably changed since the 1950""s. Another approach has been to use so-called xe2x80x9cducted rockets,xe2x80x9d which bring air into the combustion chamber via inlets and flow ducts, where the air combines with the propellant gases to increase the specific impulse of the propellant. While ducted rockets have been investigated since at least the mid 1960""s, they have never progressed beyond the prototyping stage because of their inherent difficulties and complexity. In particular, bringing air into the combustion chamber uses much available volume which could otherwise be used for propellant and subjects the duct materials to extremely harsh thermal and flow conditions. To date, no one has been able to overcome these problems with sufficient success to justify the increased cost and complexity.
The present invention, an afterburning aerospike nozzle, improves the delivered energy density of rocket motors, with less complexity than ducted rocket motors.
The invention will be better understood, and further objects, features, and advantages thereof will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings.